Systems, methods, and devices for real-time treatment verification using an electronic portal imaging device

ABSTRACT

A radiation dose received by a patient from a radiation therapy system can be verified by acquiring a cine stream of image frames from an electronic portal imaging device (EPID) that is arranged to detect radiation exiting the patient during irradiation. The cine stream of EPID image frames can be processed in real-time to form exit images providing absolute dose measurements at the EPID (dose-to-water values), which is representative of the characteristics of the radiation received by the patient. Compliance with predetermined characteristics for the field can be determined during treatment by periodically comparing the absolute dose measurements with the predetermined characteristics, which can include a predicted total dose in the field after full treatment and/or a complete irradiation area outline (CIAO). The system operator can be alerted or the irradiation automatically stopped when non-compliance is detected.

FIELD

The present disclosure relates generally to delivering radiation to apatient, and, more particularly, to systems, methods, and devices forreal-time dosimetric verification of radiation therapy treatments usingan electronic portal imaging device (EPID).

BACKGROUND

Dynamic radiation treatment techniques, such as intensity-modulatedradiation therapy (IMRT) and volumetric modulated arc therapy (VMAT),are typically used with a radiotherapy system, such as a linearaccelerator (linac), equipped with a multi-leaf collimator (MLC) totreat pathological anatomies (tumors, lesions, vascular malformations,nerve disorders, etc.) by delivering prescribed doses of radiation(X-rays, gamma rays, electrons, protons, and/or ions) to thepathological anatomy while minimizing radiation exposure to thesurrounding tissue and critical anatomical structures. Use of the MLCallows the radiotherapist to treat a patient from multiple angles whilevarying the shape and dose of the radiation beam, thereby providing agreatly enhanced ability to deliver radiation to a target within atreatment volume while avoiding excess irradiation of nearby healthytissue. IMRT and VMAT, which are complex techniques involving thesynchronous occurrence of gantry rotation, MLC motion, and dose ratemodulation, are rapidly growing as radiation therapy techniques due totheir ability to quickly deliver highly conformal dose distributions.

Quality assurance is an integral component in the workflow of clinicalradiotherapy. After creating a clinical treatment plan, the performanceof the different machine components to deliver the intended plan ischecked in a pre-treatment verification step, which confirms that thetreatment system is capable of delivering the intended dose distributionusing the installed collimation devices, e.g., jaws or MLC. Differentmeasurement methods can be applied, such as ion chamber or diode arraysthat directly measure the delivered dose distribution without thepatient in the beam and before the first treatment.

Recently, errors in the delivery of a radiation therapy have resulted ininjury to patients, some with fatal consequences, despite pre-treatmentverification. In particular, because this verification occurs withoutthe patient in place, it cannot account for changes in setup, such assystem errors or misalignment, that may inadvertently expose the patientto harmful radiation during treatment. Moreover, dose to the patient canbe affected by significant changes in patient anatomy, such as weightloss or significant tumor shrinkage. Thus, a need exists for monitoringdose delivery during treatment of the patient, to account for potentialerrors, such as missing beam limiting devices, patient positioningerrors, mismatch between treatment plan and patient, etc. and to accountfor anatomical changes.

SUMMARY

Systems, methods, and devices for real-time dosimetric verification ofradiation therapy treatments using an electronic portal imaging device(EPID) are disclosed herein. The EPID of a radiation therapy system canbe extended behind the patient. Radiation from the treatment system thatexits the patient can be detected by the EPID, which generates a cinestream of megavoltage (MV) image frames. Based on these image frames andthe resulting images, absolute dose (dose-to-water) of radiationreceived by the EPID can be calculated. These absolute dose values canbe compared in real-time against pre-determined dose distributioncharacteristics. The comparison can include a check for radiationoutside a boundary of the field at the onset of the treatment and/or anongoing check for cumulative radiation dose that exceeds a total dose tobe received by the patient for the entire treatment field. An errorsignal can be generated if the applied radiation field fails to conformto the intended dose profile. Thus, dose delivery during treatment canbe monitored in real-time in order to prevent injury to the patient.

In embodiments, a method for verifying radiation dose received by apatient from a radiation therapy system can include irradiating a fieldusing a radiation beam from the radiation therapy system. During theirradiating, a continuous stream (i.e., cine stream) of image frames canbe acquired from an EPID that is arranged to detect radiation exitingthe patient, and the cine stream of EPID image frames can be processedin real-time (e.g., by accumulating image frames over a predeterminedtime period to form respective exit images) in order to obtain dosemeasurements for the field as absolute dose-to-water values. Inaddition, during the irradiating, compliance with predeterminedcharacteristics can be determined for the field by comparing theprocessed images with the predetermined characteristics. An error signalcan be generated in response to a determination of non-compliance basedon the comparing.

In embodiments, the predetermined characteristics can include apredicted total dose in the field after the full treatment, and thecomparing can include a difference comparison between the absolute dosemeasurement and the predicted total dose. In embodiments, thepredetermined characteristics can include a complete irradiation areaoutline (CIAO) of the field and the comparing can include a geometriccomparison between the absolute dose measurements and the CIAO.

In embodiments, the acquired EPID images can be analyzed by performingat least one of a 2-D dose difference analysis and a gamma analysis. Anerror signal can be generated in response to a determination of at leastone of an underdose, an overdose, or a dose outside of CIAO based on thefurther analyzing.

In embodiments, a system can include a real-time verification device.The real-time verification device can be configured to receive acontinuous stream of exit EPID image frames and to process in real-timethe continuous stream of image frames (e.g., by accumulating imageframes over a predetermined time period to form respective exit images)in order to obtain absolute dose measurements at the EPID in a field ofa radiation therapy as dose-to-water values. The verification device canbe further configured to analyze the dose measurements with respect topredetermined characteristics for the field and to generate an errorsignal if the dose measurements are not compliant with one or more ofthe predetermined characteristics.

In embodiments, the system can include the verification device, an EPIDconfigured to generate a continuous stream of image frames, and aradiation therapy system with a source that generates a radiation beamfor irradiating the patient in performing the radiation therapy, whereinthe verification device is configured to analyze the dose measurementsin real-time during irradiation of the patient.

In embodiments, a non-transitory computer-readable medium can beprovided in combination with a computer processing system to performembodiments of the disclosed methods. The non-transitorycomputer-readable storage medium can be embodied with a sequence ofprogrammed instructions for verifying radiation dose received at an EPIDfrom a radiation therapy system. The computer processing system canexecute the sequence of programmed instructions embodied on thecomputer-readable storage medium to cause the computer processing systemto perform the method steps.

Objects and advantages of embodiments of the disclosed subject matterwill become apparent from the following description when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments will hereinafter be described with reference to theaccompanying drawings, which have not necessarily been drawn to scale.These drawings are for illustration purposes only and are not intendedto limit the scope of the present disclosure in any way. Whereapplicable, some features may not be illustrated to assist in theillustration and description of underlying features. Throughout thefigures, like reference numerals denote like elements. As used herein,various embodiments can mean one, some, or all embodiments.

FIG. 1 shows features of a radiation therapy system for irradiating apatient, according to various embodiments of the disclosed subjectmatter.

FIG. 2 shows features of a control system for real-time doseverification, according to various embodiments of the disclosed subjectmatter.

FIG. 3 shows features of dose verification at different stages oftreatment, according to various embodiments of the disclosed subjectmatter.

FIG. 4 is a process flow diagram of a dose verification method,according to various embodiments of the disclosed subject matter.

FIG. 5 shows exemplary timing of quality assurance checks during andafter treatment, according to various embodiments of the disclosedsubject matter.

FIG. 6 shows exemplary aspects of image processing associated with doseverification during and after treatment, according to variousembodiments of the disclosed subject matter.

FIG. 7 is a process flow diagram of a dose verification method with bothgeometry and overdose checks, according to various embodiments of thedisclosed subject matter.

FIG. 8 shows exemplary timing of combined quality assurance checksduring and after treatment, according to various embodiments of thedisclosed subject matter.

FIG. 9 is a process flow diagram of another dose verification method,according to various embodiments of the disclosed subject matter.

DETAILED DESCRIPTION

An electronic portal imaging device (EPID) can be used to verify thecorrect treatment of a patient by measuring the radiation that passesthrough the patient and is thus incident on the EPID (i.e., an exitimage). A cine stream of exit image frames taken during patienttreatment is processed and used to verify, in real-time or nearreal-time (e.g., less than one second), that the dose as delivered isnot harmful to the patient. As used herein, cine stream refers to acontinuous stream of image frames acquired by the EPID during acontinuous acquisition mode of operation.

For example, the EPID can run at a particular frame rate, such as butnot limited to 15 frames per second, which rate may be a configurablesetting that optimizes, among other things, imaging capabilities subjectto EPID or other hardware limitations. Image frames acquired over apredetermined time period for dosage check can be combined together(e.g., by summing) to form a single exit image, which may represent thedose reaching the EPID over that time period. For example, inembodiments, the predetermined time period is 1 second and the number ofimage frames summed together to form a single exit image is 15. Inembodiments, the predetermined time period is 5 seconds and the numberof image frames summed together to form a single exit image is 75. Ofcourse, other frame rates and accumulating time periods are alsopossible according to one or more contemplated embodiments. For example,the time period may be less than one second or greater than fiveseconds. Moreover, the frame rate may be constant (e.g., about 15 imageframes per second) or variable during a treatment.

The EPID images provide absolute dose values (i.e., dose-to-water, cGy)for the radiation received at the EPID, which eliminates potentialinaccuracies that are associated with other types of dose calculations.If the radiation dose is determined to be non-conforming, and thuspotentially harmful to the patient, an error signal can be triggered.The error signal can alert the operator and/or automatically haltirradiation of the patient.

Referring to FIG. 1, an exemplary radiation therapy treatment system 100is shown. The treatment system 100 can provide radiation therapy to apatient 110 positioned on a treatment couch 102 and can allow for theimplementation of various real-time radiation dose verificationprotocols. The radiation therapy treatment can include photon-basedradiation therapy, particle therapy, electron beam therapy, or any othertype of treatment therapy.

In an embodiment, the radiation therapy treatment system 100 includes aradiation treatment device 116, such as, but not limited to, aradiotherapy or radiosurgery device, which has a gantry 112 supporting aradiation module 114 with one or more radiation sources 106 and a linearaccelerator (linac) 104 operable to generate a beam of kilovolt (kV) ormegavolt (MV) X-ray radiation. The gantry 112 can be a ring gantry(i.e., it extends through a full 360° arc to create a complete ring orcircle), but other types of mounting arrangements may also be employed.For example, a static beam, or a C-type, partial ring gantry, or roboticarm can be used. Any other framework capable of positioning theradiation module 114 at various rotational and/or axial positionsrelative to the patient 110 may also be used.

The radiation module 114 can also include a modulation device (notshown) operable to modulate the radiation beam as well as to direct thetherapeutic radiation beam toward the patient 110 and a portion thereofthat is to be irradiated. The portion desired to be irradiated isreferred to as the target or target region or a region of interest. Thepatient 110 may have one or more regions of interest that need to beirradiated. A collimation device (not shown) may be included in themodulation device to define and adjust the size of an aperture throughwhich the radiation beam passes from source 106 to patient 110. Thecollimation device can be controlled by an actuator (not shown), whichcan be controlled by controller 120.

In an embodiment, the radiation therapy device is a kV or MV energyintensity modulated radiotherapy (IMRT) device. The intensity profilesin such a system are tailored to the treatment requirements of theindividual patient. The IMRT fields are delivered with a multi-leafcollimator (MLC), which can be a computer-controlled mechanical beamshaping device attached to the head of the linac 104 and includes anassembly of metal fingers or leaves. The MLC can be made of 120 movableleaves with 0.5 cm and/or 1.0 cm leaf width, for example. For each beamdirection, the optimized intensity profile is realized by sequentialdelivery of various subfields with optimized shapes and weights. Fromone subfield to the next, the leaves may move with the radiation beam on(i.e., dynamic multi-leaf collimation (DMLC)) or with the radiation beamoff (i.e., segmented multi-leaf collimation (SMLC)). The device 116 canalso be a tomotherapy device where intensity modulation is achieved witha binary collimator which opens and closes under computer control. Asthe gantry continuously rotates around the patient, the exposure time ofa small width of the beam can be adjusted with opening and closing ofthe binary collimator, allowing radiation to be delivered to the tumorthrough the most desirable directions and locations of the patient.

Alternatively, the device 116 can be a helical tomotherapy device, whichincludes a slip-ring rotating gantry or an intensity modulated arctherapy device (IMAT), which uses rotational cone beams of varyingshapes to achieve intensity modulation instead of rotating fan beams. Instill another alternative, the device 116 can be a simplified intensitymodulated arc therapy (SIMAT) device which uses multiple arcs, or asweeping window arc therapy device (SWAT), which sweeps the MLC leafpositions across the target planning volume (TPV) with rotation. In yetanother alternative, the device 116 can be a volumetric modulated arctherapy (VMAT) device where dose rate, beam aperture shape, and thespeed of rotation can be continuously varied to deliver the prescribeddose to the TPV. Indeed, any type of IMRT device can be employed astreatment device 116. For example, embodiments of the disclosed subjectmatter can be applied to image-guided radiation therapy (IGRT) devices.Each type of device 116 can be accompanied by a corresponding radiationplan and radiation delivery procedure.

Device 116 can include a portal dose imaging device 118 for acquiringdigital images to be used for portal dosimetry verification. The portaldose imaging device 118 can include EPID 108. The portal dose imagingdevice 118 can be placed at different locations, such as, on top of thetreatment couch 102, or attached to the accelerator head 104, forexample. The portal dose imaging device 118 can generate immediate 2-Ddigital information. For example, the imaging device 118 can include acamera-based device. The EPID 108 can also be a CCD-camera based device,which includes, in effect, an array of simultaneously integratingdosimeters with a dead time in between acquired frames of about 0.1 ms,for example. Another alternative is a flat panel imager, or amorphoussilicon EPID, which offers good image quality, high optical transferefficiency, large imaging area, and resistance to radiation.

An exemplary amorphous silicon EPID that can be used in embodiments isthe Varian aS1000 or the Varian aS500 (both sold by Varian MedicalSystems, Palo Alto, Calif.). Optionally, the EPID can includebackscatter shielding, which may assist in the calculation of absolutedose measurements at the EPID. However, EPIDs that do not usebackscatter shielding can also be employed. Any effect of backscatter onabsolute dose calculation when using EPIDs without such shielding can bemitigated or removed via image processing, for example, by using themethod described in the publication entitled “Measurement and modelingof the effect of support arm backscatter on dosimetry with a VarianEPID,” (published in Medical Physics, May 2010, 37(5): pp. 2269-78),which is incorporated by reference herein.

In general, EPID 108 has picture elements (pixels) that register theamount of radiation that falls thereon and convert the received amountof radiation into a corresponding number of electrons. The electrons areconverted into electrical signals which are further processed usingeither the imaging device 118 or controller 120. Such a configuration(i.e., digital imaging detector(s) positioned opposite the therapeuticsource(s) with the patient therebetween) provides the ability tocontinuously and immediately capture the energy and intensity of thetherapeutic radiation exiting the patient, in order to generatetwo-dimensional (2-D) exit images of digitized X-ray measurements.Because the portal dose imaging device 118 generates immediate, 2-Ddigital information, it facilitates 2-D dosimetry at any gantry angle.Thus, the techniques described above and elsewhere herein are applicableto static arc treatments as well as continuous arc and other beamdeliveries.

The controller 120 can include a computer with typical hardware such asa processor, and an operating system for running various softwareprograms and/or communication applications. The computer can includesoftware programs that operate to communicate with the radiation therapydevice 116, which software programs are operable to receive data fromexternal software programs and hardware. The computer can also includeany suitable input/output devices adapted to be accessed by medicalpersonnel, as well as input/output (I/O) interfaces, storage devices,memory, keyboard, mouse, monitor, printers, scanner, etc. The computercan also be networked with other computers and radiation therapysystems. Both the radiation therapy device 116 and the controller 120can communicate with a network as well as a database and servers. Thecontroller 120 can be configured to transfer medical image related databetween different pieces of medical equipment.

The system 100 can also include a plurality of modules containingprogrammed instructions (e.g., as part of controller 120, or as separatemodules within system 100, or integrated into other components of system100), which instructions cause system 100 to perform different functionsrelated to radiation therapy/surgery, as discussed herein, whenexecuted. For example, system 100 can include image processing andevaluation modules that provide real-time verification of the absolutedose at the EPID during irradiation. The system can also include aportal dosimetry module that provides post-treatment verification ofintended radiation dose, including a 2-D map of underdose and overdoseconditions.

The dosage measurements provided by the system 100 can be in absolutedose values (i.e., dose-to-water) at the EPID. Although the actual dosereceived by the patient is not calculated, the absolute dose at the EPIDis representative of the dose conditions received by the patient sincethe radiation received at the EPID should have passed through thepatient. Prior to treatment, the absolute dose measured by the EPID(i.e., at the plane of the EPID) is predicted. If the absolute doseactually measured by the EPID matches the predicted dose, then theconditions underlying the prediction can be presumed to match the actualtreatment conditions. Thus, dose delivery to the patient, patientanatomy, and/or patient setup can be in compliance with the originaltreatment plan. However, noncompliance of the absolute dose measurementsat the EPID as compared to the predicted dose can be indicative of someerror in radiation delivery to the patient, such as deviations ofpatient anatomy or setup from the treatment plan or an erroneousradiation therapy device configuration.

The system 100 can further include a treatment delivery module operableto instruct the radiation therapy device 116 to deliver the treatmentplan with or without the patient 110 in place, an image processingmodule operable to receive the cine stream of EPID image frames and toprocess the image frames into 2-D portal images and absolute dosevalues, and a real-time evaluation module operable to computecomparisons between predicted and measured absolute dose distributionsand to calculate radiation delivery errors. The modules can be writtenin C or C++ programming languages, for example. Computer program codefor carrying out operations as described herein may also be written inother programming languages.

Referring to FIG. 2, a controller 120 can include one or modules foroperating the radiation therapy system, for example, via irradiationbeam controller 224 and for processing the cine stream of image framesfrom EPID 108. As noted above, the processing of the cine stream caninclude accumulating image frames obtained over a set period of timeinto a single exit image. The controller 120 can communicate with aserver 202, for example, a remote server, which can include a database206 in communication with a dose prediction module 204. The doseprediction module 204 can predict various features of the radiation dosefor a specific treatment modality, such as absolute dose distributions(dose-to-water) at the EPID in each treatment field. For example, thedose prediction module 204 can be an Eclipse™ treatment planning systemand the database 206 can be part of an ARIA® oncology information system(both sold by Varian Medical Systems, Palo Alto, Calif.).

Information regarding the predicted absolute dose distributions can becommunicated from server 202 to controller 120, and in particular, thetreatment console 208 of controller 120. Alternatively or additionally,absolute dose distributions can be predicted using treatment planningmodule 212 of treatment console 208. Treatment planning module 212 mayalso determine a desired treatment plan for irradiating a patient for aparticular treatment. The treatment plan can include radiation dosageinformation and beam shape for one or more control points necessary toeffect a desired treatment of the patient. Treatment console 208 canalso include, for example, a memory module 210 for storage of doseprediction information (e.g., predicted absolute dose information and/orpredicted exit images for each field in a treatment plan) as well astreatment plan information.

A cine stream of image frames from EPID 108 can be received andprocessed by the controller 120, in particular, image processing module214. An evaluation module 216 of the controller 120 can compare theabsolute dose information to one or more characteristics of thepredicted dose for the irradiation field, for example, from treatmentconsole 208, to determine if any errors are present during treatment.Alternatively or additionally, processed images from the imageprocessing module 214 can be stored in memory module 218. The evaluationmodule 216 can use information from stored images to determinecumulative dosage information, for example. Although memory module 218and memory module 210 are shown separately, it is also possible tointegrate modules 210 and 218 together as a single memory module, or tosplit the functions of modules 210 and 218 among more than two memorymodules, according to one or more contemplated embodiments.

When the evaluation module 216 determines that an error exists, theevaluation module 216 can provide information regarding the error toprocessor 222, for example, a computer processing unit (CPU), whichgenerates an error signal. The error signal can include informationrelated to the type of error detected, such as irradiation dose outsideof intended CIAO or that accumulated dose received by the patientexceeds the total dose for that particular field. The error signal fromthe processor 222 can communicate directly with an irradiation beamcontrol unit, for example, to immediately interrupt beam irradiation ofthe patient to reduce the risk of injury to the patient. Alternativelyor additionally, the error signal can be provided to a display 226, forindicating the presence and nature of the error to the treatment systemoperator. For example, the display 226 can illustrate the deviation ofthe radiation dose from predictions on one of the EPID exit images, suchas indicating a region where the accumulated dose exceeds a total doseor where the dose is outside the CIAO. If the system operator determinesthat the error is a false alarm or otherwise will not negatively affectthe patient's treatment, the operator may override the error usinginput/output module 228 and thereby allow treatment to continue.

After the field is completed, for example, immediately after terminationof irradiation for that field, the EPID images stored in memory module218 can be processed by portal dosimetry module 220. Portal dosimetrymodule 220 can perform a full portal dosimetry analysis on the acquiredimages, e.g., a more processing intensive 2-D analysis to determineregions of underdose, overdose, or other deviations in the radiationfield. For example, the portal dosimetry module (as well as the variousdescriptions of portal dosimetry described herein) can be Varian'sPortal Dosimetry product (sold by Varian Medical Systems, Palo Alto,Calif.). When the portal dosimetry module 220 determines that an errorexists, it can provide information regarding the error to processor 222,which generates an error signal. The error signal can includeinformation related to the type of error detected, such as underdose oroverdose conditions for a region of the field. The error signal from theprocessor 222 can communicate directly with an irradiation beam controlunit, for example, to provide an interlock that prevents furtherirradiation of the patient. Alternatively or additionally, the errorsignal can be provided to a display 226, for indicating the presence andthe nature of the error to the treatment system operator. For example,the display 226 can illustrate regions of underdose or overdose on oneof the EPID exit images. If the system operator determines that theerror is a false alarm or otherwise will not negatively affect thepatient's treatment, the operator may override the interlock usinginput/output module 228 in order to proceed with a subsequent radiationfield.

FIG. 3 illustrates various high-level features of the discloseddosimetric verification that can reduce the risk of injury to thepatient. The dosimetric verification can include a pre-irradiationregimen 302, a regimen concurrent with irradiation 308, and apost-irradiation regimen 314. The pre-irradiation regimen 302 caninclude calibration 304 of the EPID, in particular, such that itproduces absolute dose measurements (dose-to-water (cGy)) for all fieldgeometries and at all points of the EPID. Such calibration techniquesfor producing absolute dose information from exit EPID images are knownin the art, and one of ordinary skill in the art can readily producesuch results based on, for example, the publication entitled, “A globalcalibration model for a-Si EPIDs used for transit dosimetry,” (publishedin Medical Physics, October 2007, 34(10): pp. 3872-84), which isincorporated by reference herein.

The pre-irradiation regimen 302 can also include prediction 306. Forexample, the dose prediction module 204 can be used in prediction 306 topredict various features of the radiation dose for a specific treatmentmodality, such as absolute dose distributions (dose-to-water) at theEPID for each treatment field. Prediction 306 can also includeconfigurations for one or more radiation fields, for example, to effecta desired radiation treatment. Information regarding calibration 304 andprediction 306 can be used during the irradiation regimen 308 to enablereal-time dose verification.

During the irradiation regimen 308, the system can acquire image framesfrom the EPID in real-time, i.e., via a cine mode image acquisition 310,which can be performed, for example, by image processing module 214. Theimage acquisition 310 can also involve correction of the acquired imageframes, for example, to account for positioning variations (e.g.,positioning of the EPID) or backscatter. Subsequently, the image framescan be processed and analyzed, for example, by evaluation module 216, toform an exit image and to determine whether there are any errors in theirradiation dose. In particular, image processing and analysis regimen312 can include converting the images to provide a measure of absolutedose (dose-to-water) at the EPID.

The image processing and analysis 312 can be configured to process theimage frames and provide an evaluation in real-time or near real-time(e.g., less than one second). For example, the analysis 312 can involvethe evaluation of absolute dose measurement to determine if theirradiation (or radiation exceeding a predetermined safe threshold) isoutside the desired CIAO at the beginning of the treatment to avoidpotential injury to healthy tissue of the patient. Such an initialanalysis can provide an indication of major problems associated with theirradiation, for example, a missing MLC.

Alternatively or additionally, the analysis 312 can involve theevaluation of absolute dose measurements to determine if a cumulativedose received by the patient exceeds a total planned dose for theparticular field. To this end, a difference calculation (i.e.,determining if a dose exceeds a common maximum value at any point in theirradiation field) can be used, which reduces processing time and canallow for real-time (or near real-time) dose evaluation. Such ananalysis can occur at regular intervals during irradiation (e.g., everyfive seconds after initiation of irradiation) and can detect lesssignificant anomalies, for example, a stuck MLC leaf or a beam steeringproblem. Alternatively, such an analysis can be performed at regularintervals during radiation together with the above analysis with respectto the CIAO, either simultaneously or sequentially. By virtue of thisreal-time evaluation of absolute dose information, any damage that mayresult from improper irradiation of the patient can thus be minimized,or at least reduced.

The processed images can also be used in post-irradiation regimen 314.For example, images obtained from the EPID during irradiation (e.g., viacine mode image acquisition 310) can be employed in a full portaldosimetry analysis 316. The portal dosimetry analysis 316 can beperformed, for example, by portal dosimetry module 220 of controller120. Timing of the analysis is less of an issue to prevent immediateinjury to the patient since irradiation has already been completed.Therefore, full portal dosimetry analysis 316 can involve moretime-intensive processing to determine conditions of both underdose andoverdose at each point in the CIAO. For example, difference and gammaprocessing can be employed to produce a full 2-D analysis of themeasured absolute dose based on the exit images obtained by the EPID. Ifthe analysis indicates that an error is present (e.g., conditions ofoverdose that may pose a risk of injury to the patient should radiationtreatment continue), an interlock can be asserted to prevent furthertreatment (i.e., prevent proceeding to the next irradiation field),subject to override by a system operator.

Referring to FIG. 4, a process flow diagram of an exemplary dosimetricverification method is shown. At 402, the EPID is calibrated to provideabsolute dose measurements (dose-to-water) of the radiation at the EPIDbased on exit images obtained during irradiation of the patient.Calibration to provide absolute dose measurements can be performed asdescribed in the incorporated by reference October 2007 publicationnoted above. At 404, a treatment plan can be generated that predicts theabsolute dose values for each irradiation field. The geometry of theCIAO and the total absolute dose (i.e., the maximum cumulative dose forthe irradiation field) are noted for dose verification during theirradiation.

At 406, the system can be configured for a particular irradiation field.For example, the patient can be positioned on the treatment couch. TheEPID can then be extended and positioned with respect to the patient inorder to detect an exit image, i.e., to detect radiation from theradiation system that has passed through the patient. The radiationsystem can then be configured for a particular irradiation field, forexample, by positioning the MLC or beam steering components to provide adesired CIAO.

After configuration for the irradiation field is complete, the radiationbeam is turned on at 408. An initial check of the irradiation field canbe performed at 410. For example, at one second after the initiation ofirradiation (i.e., when t=t₁=1 s), it is determined at 412 if theapplied irradiation field complies with the desired CIAO for the field(i.e., geometry check). If radiation (or radiation exceeding a safethreshold) is received outside of the CIAO, it may damage healthy tissueor otherwise injure the patient. Thus, the initial check should beperformed before any significant damage to the patient may occur. Whileit is unlikely that a sufficiently harmful dose will be delivered to thepatient by errant field geometry during the first second after beaminitiation, other time periods, either shorter or longer, for theinitial evaluation are also possible according to one or morecontemplated embodiments.

If the exit image analysis indicates that a dose is received outside ofthe CIAO, a determination of an error based on position or geometry ismade at 414 and an error signal can be generated at 416. The errorsignal may result in automatic shut-off of the radiation field at 418and/or notification to the radiation system operator of the error at420. The notification to the radiation system operator at 420 can be inthe form of a general error indication (e.g., visual or audio alarm, oron-screen pop-up notification, that an error exists), a specific errorindication (e.g., description of the nature of the error), or agraphical error indication (e.g., a graphical representation on an exitimage obtained by the EPID).

If the dose is determined to be compliant with the desired CIAO at 412,irradiation can continue subject to an ongoing evaluation for overdose.Such an evaluation may be performed periodically or continuously.Processing of the image frames for determination of cumulative absolutedose may be configured to occur in real-time or near-real time (e.g.,less than one second). Should the cumulative dose at any point in timeexceed the total dose planned for the treatment field, furtherirradiation beyond this point may result in harm to the patient. Thus,the ongoing check monitors the absolute dose received at the EPID(determined by the EPID exit images) in order to respond to conditionsof potential overdose, for example, by terminating irradiation of aparticular field earlier than anticipated.

The evaluation of the images may occur at discrete time periods toreduce the amount of processing involved without substantiallyincreasing the risk of injury to the patient. For example, every fiveseconds after the initiation of irradiation (i.e., when t=n×t₂=n×5 s) asdetermined at 422, an evaluation of the cumulative dose with respect toa total dose for the irradiation field is performed at 424 (i.e.,overdose check). However, other time periods, either shorter or longer,for the ongoing evaluation are also possible according to one or morecontemplated embodiments. For example, there may be periods duringtreatment where irradiation is temporarily suspended, such as by gatingor during beam-off periods due to patient motion or planned beam breaksin the treatment plan. Embodiments of the disclosed methods and systemscan recognize and take advantage of such irradiation suspension events,for example, to process data to catch up on an evaluation of dosedelivery compliance with a plan, especially if such evaluations arecomputationally intensive.

FIG. 5 shows an exemplary time line for different dose verificationanalyses. For example, one second after initiation of irradiation for aparticular field, a geometry check 502 that compares the irradiationfield to the desired CIAO is performed (i.e., 412 in FIG. 4). If noerrors are indicated or irradiation continues, then an overdose check504 ₁ can be performed at five seconds after initiation of irradiationfor the particular field (i.e., 424 in FIG. 4). If no errors areindicated or irradiation continues, a second overdose check 504 ₂ can beperformed at ten seconds, a third overdose check 504 ₃ can be performedat fifteen seconds, and additional overdose checks 504 _(n) can beperformed at each five second interval 5n until irradiation terminates.Such time periods for the geometry and overdose checks are merelyexemplary and other time periods are also contemplated. The geometryand/or overdose checks can take the form of a difference calculationwith respect to predetermined absolute dose values.

Returning to FIG. 4, if the exit image evaluation at 424 indicates thatthe absolute dose at any point in the CIAO exceeds the total dose, adetermination of an error based on overdose is made at 426 and an errorsignal can be generated at 416. As noted above, the error signal mayresult in automatic shut-off of the radiation field at 418 and/ornotification to the radiation system operator of the error at 420. Theevaluation at 424 can be repeated (via 422) until the irradiation forthe field is complete.

Once the field is determined to b complete at 428, the radiation beam isturned off at 430. Subsequently, full portal dosimetry can be performedat 432, which can involve, for example, difference and gamma processing(see also 506 in FIG. 5) to produce a full 2-D analysis of the measuredexit dose, in absolute dose values. If the 2-D analysis reveals that thedose delivered to the patient is non-compliant at 434, a determinationof an error based on overdose or underdose is made at 436 and an errorsignal can be generated at 438. For example, if the analysis valuesexceed pre-defined action levels with respect to a predeterminedabsolute dose map (e.g., a percentage over or under the desiredcumulative dose at that particular point of the EPID), then adetermination of non-compliance can be made and an error signalgenerated. As noted above, the error signal may result in notificationto the radiation system operator of the error at 420. Alternatively oradditionally, the error signal at 438 can produce an interlock at 440that prevents further irradiation fields, which interlock can beoverridden by an operator to continue treatment.

If the 2-D analysis reveals that the dose delivered to the patient iscompliant at 434, it is determined if additional radiation fields aredesired at 442. However, if the analysis reveals that an underdose wasdelivered, additional radiation fields can be determined to deliver thedesired dose. If no further fields are needed, the treatment terminatesat 444. Otherwise, the process can repeat by returning to 406 toconfigure the patient and the radiation system for the next radiationfield.

FIG. 6 is a diagram summarizing aspects of the image acquisition andprocessing for dose verification. Image frames obtained by the EPID areacquired (602), which are then corrected for EPID position variations(604). The image frames are then processed to produce an exit image,which is further processed to yield absolute dose values (606) based oncalibration of the EPID. The absolute dose values can be used forvarious analyses (608) during and after irradiation. For example, theabsolute dose measurements are used during an initial time period afterthe start of treatment to confirm compliance of the irradiation beamwith the desired CIAO (610). The absolute dose measurements acquired canalso be used to provide an ongoing verification that the absolute dosereceived by the patient does not exceed a planned total dose for thefield, for example, by a difference calculation (612). Afterirradiation, a more comprehensive analysis of the absolute dose valuesand/or EPID exit images can be performed to determine 2-D compliance ofthe irradiation with a pre-treatment plan. Thus, a 2-D difference andgamma calculations can be performed (614).

Although not illustrated in FIG. 6, the geometry (610) and difference(612) calculations can be combined such that both checks, or alternatingchecks, are performed at the beginning of treatment and periodicallyduring treatment. For example, instead of just an initial geometry checkand subsequent overdose checks, the initial check may include otherchecks in addition to the geometry check while subsequent periodicchecks can include other checks in place of or in addition to theoverdose check. The process flow diagram of FIG. 7 reflects such anembodiment.

Referring to FIG. 7, a process flow diagram of another exemplarydosimetric verification method is shown. At 702, the EPID is calibratedto provide absolute dose measurements (dose-to-water) of the radiationat the EPID based on exit images obtained during irradiation of thepatient. Calibration to provide absolute dose measurements can beperformed as described in the incorporated by reference October 2007publication noted above. At 704, a treatment plan can be generated thatpredicts the absolute dose values at the EPID for each irradiationfield. The geometry of the CIAO and the total absolute dose (i.e., themaximum cumulative dose for the irradiation field) are noted for doseverification during the irradiation.

At 706, the system can be configured for a particular irradiation field.For example, the patient can be positioned on the treatment couch. TheEPID can then be extended and positioned with respect to the patient inorder to detect exit image frames, i.e., to detect radiation from theradiation system that has passed through the patient. The radiationsystem can then be configured for a particular irradiation field, forexample, by positioning the MLC or beam limiting components to provide adesired CIAO.

After configuration for the irradiation field is complete, the radiationbeam is turned on at 708. An initial check of the irradiation field canbe performed at 710. For example, at one second after the initiation ofirradiation (i.e., when t=t₁=1 s), it is determined at 712 if theapplied irradiation field complies with the desired CIAO for the field.If the exit image analysis indicates that a dose is received outside ofthe CIAO, a determination of an error based on position or geometry ismade at 714 and an error signal can be generated at 716. The errorsignal may result in automatic shut-off of the radiation field at 718and/or notification to the radiation system operator of the error at720. The notification to the radiation system operator at 720 can be inthe form of a general error indication (e.g., visual or audio alarm, oron-screen pop-up notification, that an error exists), a specific errorindication (e.g., description of the nature of the error), or agraphical error indication (e.g., a graphical representation on an exitimage obtained by the EPID).

Subsequently or concurrently, an evaluation of the cumulative absolutedose received at the EPID with respect to the predicted total dose forthe irradiation field is performed at 724. If the exit image evaluationat 724 indicates that the absolute dose at any point in the CIAO exceedsthe total dose, a determination of an error based on overdose is made at726 and an error signal can be generated at 716. As noted above, theerror signal may result in automatic shut-off of the radiation field at718 and/or notification to the radiation system operator of the error at720.

If the dose is determined to be compliant with both the desired CIAO at712 and total dose at 724, irradiation can continue subject to periodiccompliance evaluation (i.e., the geometry check at 712 and the totaldose at 724). Such an evaluation may be performed periodically orcontinuously. For example, the evaluation of exit images for geometryand total dose compliance may occur at discrete periodic time periods toreduce the amount of processing involved without substantiallyincreasing the risk of injury to the patient, for example, every fiveseconds after the initiation of irradiation (i.e., when t=n×t₂=n×5 s) asdetermined at 710. However, other time periods, either shorter orlonger, for the ongoing evaluation are also possible according to one ormore contemplated embodiments.

FIG. 8 shows an exemplary time line for different dose verificationanalyses. For example, one second after initiation of irradiation for aparticular field, a geometry check 802 that compares the irradiationfield to the desired CIAO is performed (i.e., 712 in FIG. 7). Theinitial check 802 can also include an overdose check (i.e., 724 in FIG.7). If no errors are indicated or irradiation continues, then an ongoingcheck 804 _(n) can be performed at five second intervals afterinitiation of irradiation for the particular field. For example, eachongoing check 804 _(n) can include an overdose check (i.e., 724 in FIG.7) and a geometry check (i.e., 712 in FIG. 7). Alternatively, theongoing checks 804 _(n) can alternate between the overdose check and thegeometry check. For example, ongoing check 804 ₁ can be an overdosecheck, ongoing check 804 ₂ can be a geometry check, ongoing check 804 ₃can be another overdose check, and so on.

If no errors are indicated or irradiation continues after the firstongoing check 804 ₁, a second check 804 ₂ can be performed at tenseconds, a third overdose check 804 ₃ can be performed at fifteenseconds, and additional overdose checks 804 _(n) can be performed ateach five second interval (i.e., 5n) until irradiation terminates. Suchtime periods for the geometry and overdose checks are merely exemplaryand other time periods are also contemplated. The geometry and/oroverdose checks can take the form of a difference calculation withrespect to predetermined absolute dose values at the EPID.

Returning to FIG. 7, once the field is determined to be complete at 728,the radiation beam is turned off at 730. Subsequently, full portaldosimetry can be performed at 732, which can involve, for example,difference and gamma processing (see also 806 in FIG. 8) to produce afull 2-D analysis of the measured exit dose, in absolute dose values. Ifthe 2-D analysis reveals that the dose delivered to the patient isnon-compliant at 734, a determination of an error based on overdose orunderdose is made at 736 and an error signal can be generated at 738.For example, if the analysis values exceed pre-defined action levelswith respect to a predetermined absolute dose map (e.g., a percentageover or under the desired cumulative dose at that particular point ofthe EPID), then a determination of non-compliance can be made and anerror signal generated. As noted above, the error signal may result innotification to the radiation system operator of the error at 720.Alternatively or additionally, the error signal at 738 can produce aninterlock at 740 that prevents further irradiation fields, whichinterlock can be overridden by an operator to continue treatment.

If the 2-D analysis reveals that the dose delivered to the patient iscompliant at 734, it is determined if additional radiation fields aredesired at 742. If no further fields are needed, the treatmentterminates at 744. Otherwise, the process can repeat by returning to 706to configure the patient and the radiation system for the next radiationfield.

In embodiments, predictions for the absolute dose at the EPID for thetotal field are employed. Predictions for individual treatment framesare not needed, thereby reducing the computational resources that mayotherwise be required. In addition, synchronization of the predictionwith the treatment, i.e., based on the MLC shape, is not necessary sincethe prediction employed is for the total field and not individualframes. Thus, the above-described embodiments can be applicable to anyradiation treatment type, not just IMRT treatments.

Although embodiments have been described where simplified comparisons ofabsolute dose measurements are performed during irradiation to reducethe amount of processing power and time required, more complexcomparisons can also be performed during irradiation according to one ormore contemplated embodiments. For example, instead of calibrating theEPID and processing images to yield absolute dose values, thepre-treatment calculations can predict the radiation image in theamorphous silicon of the EPID after having passed through the patient.The process flow diagram of FIG. 9 reflects such an embodiment.

At 902, a treatment plan is generated that predicts the exit dose in theamorphous silicon of the EPID after the radiation has passed through thepatient. At 906, the system can be configured for a particularirradiation field. For example, the patient can be positioned on thetreatment couch. The EPID can then be extended and positioned withrespect to the patient in order to detect exit image frames, i.e., todetect radiation from the radiation system that has passed through thepatient. The radiation system can then be configured for a particularirradiation field, for example, by positioning the MLC or beam steeringcomponents to provide a desired CIAO.

After configuration for the irradiation field is complete, the radiationbeam is turned on at 908. An ongoing evaluation for compliance with thedesired dose profile can be performed. Such an evaluation may beperformed periodically (e.g., every five seconds) or continuously.Processing of the image frames for determination of compliance may beconfigured to occur in real-time or near-real time (e.g., less than onesecond). However, the evaluation of the images may occur at discretetime periods to reduce the amount of processing involved withoutsubstantially increasing the risk of injury to the patient. For example,every second after the initiation of irradiation (i.e., when t=n×t₁=n×1s) as determined at 910, a comparison of the radiation image in theamorphous silicon of the EPID to the predicted radiation image for theirradiation field can be made at 912. Such a comparison can include, butis not limited to, a full portal dosimetry analysis, e.g., includingdifference and/or gamma processing, as time will allow.

If the comparison at 912 indicates that the dose is not compliant (e.g.,due to overdose, underdose, or dose outside of CIAO) at 914, an errorsignal can be generated at 916. The error signal may result in automaticshut-off of the radiation field at 918 and/or notification to theradiation system operator of the error at 920. The notification to theradiation system operator at 920 can be in the form of a general errorindication (e.g., visual or audio alarm, or on-screen pop-upnotification, that an error exists), a specific error indication (e.g.,description of the nature of the error), or a graphical error indication(e.g., a graphical representation on an exit image obtained by theEPID).

Once the field is determined to be complete at 922, the radiation beamis turned off at 924. Optionally, full portal dosimetry can be performedat 926, which can involve difference and gamma processing to produce afull 2-D analysis of the measured images. If the 2-D analysis revealsthat the radiation images are non-compliant at 928, a determination ofan error based on overdose or underdose is made at 930 and an errorsignal can be generated at 932. For example, if the values exceedpre-defined action levels with respect to a predetermined dose map(e.g., a percentage over or under the desired cumulative dose at thatparticular point of the EPID), then a determination of non-compliancecan be made and an error signal generated. As noted above, the errorsignal may result in notification to the radiation system operator ofthe error at 920. Alternatively or additionally, the error signal at 932can produce an interlock at 934 that prevents further irradiationfields, which interlock can be overridden by an operator to continuetreatment.

If the 2-D analysis reveals that the radiation images are compliant at928, it is determined if additional radiation fields are desired at 936.If no further fields are needed, the treatment terminates at 938.Otherwise, the process can repeat by returning to 906 to configure thepatient and the radiation system for the next radiation field.

In one or more embodiments of the disclosed subject matter, methods forverifying radiation dose received by a patient from a radiation therapysystem are provided. The methods can include irradiating a field using aradiation beam from the radiation therapy system. The methods can alsoinclude, during the irradiating, acquiring a continuous stream of imageframes from an EPID (i.e., a cine stream) that is arranged to detectradiation exiting the patient. The methods can further include, duringthe irradiating, processing the stream of image frames in real-time toobtain absolute dose measurements at the EPID in the field asdose-to-water values, and determining compliance with predeterminedcharacteristics for the field by comparing the processed images with thepredetermined characteristics. The methods can additionally includegenerating an error signal in response to a determination ofnon-compliance based on the comparing.

In one or more embodiments of the disclosed subject matter, thecontinuous stream of EPID images can be MV images. In one or moreembodiments of the disclosed subject matter, the EPID can includebackscatter shielding. In one or more embodiments of the disclosedsubject matter, the EPID does not have backscatter shielding and theprocessing includes correcting the EPID images for backscatter. In oneor more embodiments of the disclosed subject matter, the predeterminedcharacteristics can include a predicted total dose in the field afterthe full treatment, and the comparing can be a difference comparisonbetween the absolute dose measurement and the predicted total dose. Inone or more embodiments of the disclosed subject matter, a determinationof non-compliance based on overdose can be made in response to anabsolute dose measurement exceeding the predicted total dose. In one ormore embodiments of the disclosed subject matter, the determiningcompliance can be repeated at regular intervals after initiation of theirradiating, for example, at regular intervals no more than five secondsapart.

In one or more embodiments of the disclosed subject matter, thepredetermined characteristics can include a CIAO of the field, and thecomparing can be a geometric comparison between the absolute dosemeasurements and the CIAO. In one or more embodiments of the disclosedsubject matter, a determination of non-compliance based on positioningcan be made in response to an absolute dose measurement being outsidethe CIAO. In one or more embodiments of the disclosed subject matter,the determining compliance can be performed within one second afterinitiation of the irradiating.

In one or more embodiments of the disclosed subject matter, a time fromthe processing of images to the generating an error signal does notexceed one second. In one or more embodiments of the disclosed subjectmatter, the error signal can be an alert to an operator of the radiationtherapy system. In one or more embodiments of the disclosed subjectmatter, the error signal can be a shutoff signal to the radiationtherapy system which turns off the radiation beam.

In one or more embodiments of the disclosed subject matter, the methodscan include, after the irradiating, further analyzing the acquired EPIDimages by performing at least one of a 2-D dose difference analysis anda gamma analysis. In one or more embodiments of the disclosed subjectmatter, a second error signal can be generated in response to adetermination of at least one of an underdose, overdose, or dose outsideof CIAO based on the further analyzing. In one or more embodiments ofthe disclosed subject matter, the second error signal can be an alert toan operator of the radiation therapy system or an interlock thatprevents further irradiation using the radiation therapy system

In one or more embodiments of the disclosed subject matter, the methodscan include, prior to the irradiating, predicting the total exit doseimage, in absolute dose-to-water, for the field. In one or moreembodiments of the disclosed subject matter, a graphical representationof the noncompliance can be displayed on one of the EPID images.

In one or more embodiments of the disclosed subject matter, systems caninclude a real-time verification device configured to receive acontinuous stream of exit image frames (i.e., cine stream) and toprocess in real-time the continuous stream of image frames so as toobtain absolute dose measurements at an imaging device in a field of aradiation therapy as dose-to-water values. In one or more embodiments ofthe disclosed subject matter, the verification device can be configuredto analyze the dose measurements with respect to predeterminedcharacteristics for the field and to generate an error signal if thedose measurements are not compliant with one or more of thepredetermined characteristics.

In one or more embodiments of the disclosed subject matter, systems caninclude an EPID as the imaging device, the EPID being configured togenerate said continuous stream of images by detecting radiation exitinga patient. In one or more embodiments of the disclosed subject matter,the EPID can include backscatter shielding. In one or more embodimentsof the disclosed subject matter, the EPID has no backscatter shieldingand the system is configured to correct EPID images for backscatter.

In one or more embodiments of the disclosed subject matter, systems caninclude a radiation therapy device or system with a source thatgenerates a radiation beam for irradiating the patient in performing theradiation therapy. In one or more embodiments of the disclosed subjectmatter, the verification device can be configured to analyze the dosemeasurements during irradiation of the patient. In one or moreembodiments of the disclosed subject matter, the radiation therapydevice or system can be configured to cease irradiation in response tosaid error signal.

In one or more embodiments of the disclosed subject matter, systems caninclude a memory for storage of the processed continuous stream of imageframes and for storage of a total exit dose image or value. In one ormore embodiments of the disclosed subject matter, systems can include adisplay device operatively coupled to the verification device andconfigured to display a graphical representation of non-compliance on anexit dose image.

In one or more embodiments of the disclosed subject matter, a portaldosimetry module can be configured to analyze one of the exit images byperforming at least one of a 2-D dose difference analysis and a gammaanalysis.

In one or more embodiments of the disclosed subject matter,non-transitory computer-readable storage media and a computer processingsystems can be provided. In one or more embodiments of the disclosedsubject matter, non-transitory computer-readable storage media can beembodied with a sequence of programmed instructions for verifyingradiation dose received at an EPID from a radiation therapy system, thesequence of programmed instructions embodied on the computer-readablestorage medium causing the computer processing systems to perform one ormore of the disclosed methods.

It will be appreciated that the modules, processes, systems, and devicesdescribed above can be implemented in hardware, hardware programmed bysoftware, software instruction stored on a non-transitory computerreadable medium or a combination of the above. For example, a method forradiation dose verification can be implemented, for example, using aprocessor configured to execute a sequence of programmed instructionsstored on a non-transitory computer readable medium. For example, theprocessor can include, but is not limited to, a personal computer orworkstation or other such computing system that includes a processor,microprocessor, microcontroller device, or is comprised of control logicincluding integrated circuits such as, for example, an ApplicationSpecific Integrated Circuit (ASIC). The instructions can be compiledfrom source code instructions provided in accordance with a programminglanguage such as Java, C++, C#.net or the like. The instructions canalso comprise code and data objects provided in accordance with, forexample, the Visual Basic™ language, LabVIEW, or another structured orobject-oriented programming language. The sequence of programmedinstructions and data associated therewith can be stored in anon-transitory computer-readable medium such as a computer memory orstorage device which may be any suitable memory apparatus, such as, butnot limited to read-only memory (ROM), programmable read-only memory(PROM), electrically erasable programmable read-only memory (EEPROM),random-access memory (RAM), flash memory, disk drive and the like.

Furthermore, the modules, processes, systems, and devices can beimplemented as a single processor or as a distributed processor.Further, it should be appreciated that the steps mentioned herein may beperformed on a single or distributed processor (single and/ormulti-core). Also, the processes, modules, and sub-modules described inthe various figures of and for embodiments herein may be distributedacross multiple computers or systems or may be co-located in a singleprocessor or system. Exemplary structural embodiment alternativessuitable for implementing the modules, sections, systems, means, orprocesses described herein are provided below.

The modules, processes, systems, and devices described above can beimplemented as a programmed general purpose computer, an electronicdevice programmed with microcode, a hard-wired analog logic circuit,software stored on a computer-readable medium or signal, an opticalcomputing device, a networked system of electronic and/or opticaldevices, a special purpose computing device, an integrated circuitdevice, a semiconductor chip, and a software module or object stored ona computer-readable medium or signal, for example.

Embodiments of the methods, processes, modules, devices, and systems (ortheir sub-components or modules), may be implemented on ageneral-purpose computer, a special-purpose computer, a programmedmicroprocessor or microcontroller and peripheral integrated circuitelement, an ASIC or other integrated circuit, a digital signalprocessor, a hardwired electronic or logic circuit such as a discreteelement circuit, a programmed logic circuit such as a programmable logicdevice (PLD), programmable logic array (PLA), field-programmable gatearray (FPGA), programmable array logic (PAL) device, or the like. Ingeneral, any process capable of implementing the functions or stepsdescribed herein can be used to implement embodiments of the methods,systems, or a computer program products (software program stored on anon-transitory computer readable medium).

Furthermore, embodiments of the disclosed methods, processes, modules,devices, systems, and computer program product may be readilyimplemented, fully or partially, in software using, for example, objector object-oriented software development environments that provideportable source code that can be used on a variety of computerplatforms. Alternatively, embodiments of the disclosed methods,processes, modules, devices, systems, and computer program product canbe implemented partially or fully in hardware using, for example,standard logic circuits or a very-large-scale integration (VLSI) design.Other hardware or software can be used to implement embodimentsdepending on the speed and/or efficiency requirements of the systems,the particular function, and/or particular software or hardware system,microprocessor, or microcomputer being utilized. Embodiments of themethods, processes, modules, devices, systems, and computer programproduct can be implemented in hardware and/or software using any knownor later developed systems or structures, devices and/or software bythose of ordinary skill in the applicable art from the functiondescription provided herein and with a general basic knowledge ofradiation therapy systems, control systems, and/or computer programmingarts.

Features of the disclosed embodiments may be combined, rearranged,omitted, etc., within the scope of the invention to produce additionalembodiments. Furthermore, certain features may sometimes be used toadvantage without a corresponding use of other features.

It is thus apparent that there is provided in accordance with thepresent disclosure, system, methods, and devices for radiation doseverification. Many alternatives, modifications, and variations areenabled by the present disclosure. While specific embodiments have beenshown and described in detail to illustrate the application of theprinciples of the present invention, it will be understood that theinvention may be embodied otherwise without departing from suchprinciples. Accordingly, Applicants intend to embrace all suchalternatives, modifications, equivalents, and variations that are withinthe spirit and scope of the present invention.

The invention claimed is:
 1. A method for verifying radiation dosereceived by a patient from a radiation therapy system, the methodcomprising: irradiating a field using a radiation beam from theradiation therapy system; during the irradiating, acquiring a continuousstream of image frames from an electronic portal imaging device (EPID)that is arranged to detect radiation exiting the patient; during theirradiating, processing the stream of image frames in real-time toobtain dose measurements at the EPID in the field as dose-to-watervalues; during the irradiating, determining compliance withpredetermined characteristics for the field by comparing the processedimage frames with the predetermined characteristics; and generating anerror signal in response to a determination of non-compliance based onthe comparing.
 2. The method of claim 1, wherein the continuous streamof image frames comprises megavoltage (MV) images.
 3. The method ofclaim 1, wherein the EPID includes backscatter shielding.
 4. The methodof claim 1, wherein the processing to obtain dose measurements includescorrecting the image frames for backscatter in the EPID.
 5. The methodof claim 1, wherein the predetermined characteristics include apredicted total dose in the field after the full treatment, and thecomparing comprises a difference comparison between the dosemeasurements and the predicted total dose.
 6. The method of claim 5,wherein a determination of non-compliance based on overdose is made inresponse to one of dose measurements exceeding the predicted total dose.7. The method of claim 5, wherein the predetermined characteristicsfurther include a complete irradiation area outline (CIAO) of the field,and the comparing further comprises a geometric comparison between thedose measurements and the CIAO.
 8. The method of claim 7, wherein thedetermining compliance is repeated at regular intervals after initiationof the irradiating, and at least one of the geometric and differencecomparisons is performed at each of the regular intervals.
 9. The methodof claim 1, wherein the determining compliance is repeated at regularintervals after initiation of the irradiating.
 10. The method of claim9, wherein the regular intervals are no more than five seconds apart.11. The method of claim 1, wherein the predetermined characteristicsinclude a complete irradiation area outline (CIAO) of the field, and thecomparing comprises a geometric comparison between the dose measurementsand the CIAO.
 12. The method of claim 11, wherein a determination ofnon-compliance based on positioning is made in response to dosemeasurements outside the CIAO.
 13. The method of claim 11, wherein thedetermining compliance is performed within one second after initiationof the irradiating.
 14. The method of claim 1, wherein: thepredetermined characteristics include a predicted total dose in thefield after the full treatment and a complete irradiation area outline(CIAO) of the field, the comparing comprises a difference comparisonbetween the dose measurement and the predicted total dose, and ageometric comparison between the dose measurements and the CIAO, adetermination of non-compliance based on overdose is made in response toa dose measurement exceeding the predicted total dose, and adetermination of non-compliance based on positioning is made in responseto a dose measurement being outside the CIAO.
 15. The method of claim 1,wherein a time from the processing of the stream of image frames to thegenerating an error signal does not exceed one second.
 16. The method ofclaim 1, wherein the error signal comprises at least one of an alert toan operator of the radiation therapy system and a shutoff signal to theradiation therapy system which turns off the radiation beam.
 17. Themethod of claim 1, further comprising: after the irradiating, furtheranalyzing the acquired EPID images by performing at least one of a 2-Ddose difference analysis and a gamma analysis; and generating a seconderror signal in response to a determination of at least one of anunderdose, overdose, or dose outside of CIAO based on the furtheranalyzing.
 18. The method of claim 17, wherein the second error signalcomprises an alert to an operator of the radiation therapy system or aninterlock that prevents further irradiation of the patient using theradiation therapy system.
 19. The method of claim 1, further comprising,prior to the irradiating, predicting the total exit dose image, indose-to-water, for the field.
 20. The method of claim 1, furthercomprising displaying a graphical representation of the noncompliance onan EPID image.
 21. The method of claim 1, wherein the processing thestream of image frames obtains absolute dose measurements at the EPID inthe field.
 22. A system comprising: a real-time verification deviceconfigured to receive a stream of exit image frames and to process inreal-time the stream of image frames so as to obtain dose measurementsat an imaging device for a field of a radiation therapy as dose-to-watervalues, wherein the verification device is further configured to analyzethe dose measurements with respect to predetermined characteristics forthe field and to generate an error signal if the dose measurements arenot compliant with one or more of the predetermined characteristics. 23.The system of claim 22, further comprising an electronic portal imagingdevice (EPID) as the imaging device, wherein the EPID is configured togenerate said stream of image frames by detecting radiation exiting apatient, the EPID including backscatter shielding.
 24. The system ofclaim 22, further comprising an electronic portal imaging device (EPID)as the imaging device, wherein the EPID is configured to generate saidstream of image frames by detecting radiation exiting a patient, whereinthe verification device is configured to correct the images forbackscatter in the EPID.
 25. The system of claim 22, further comprisinga radiation therapy system with a source that generates a radiation beamfor irradiating the patient in performing the radiation therapy, whereinthe verification device is configured to analyze the dose measurementsduring irradiation of the patient.
 26. The system of claim 25, whereinthe radiation therapy system is configured to cease irradiation inresponse to said error signal.
 27. The system of claim 22, furthercomprising a memory system including one or more memory modules forstorage of the processed stream of images and for storage of a totalexit dose image.
 28. The system of claim 22, further comprising adisplay device operatively coupled to the verification device andconfigured to display a graphical representation of non-compliance on anexit dose image.
 29. The system of claim 22, further comprising a portaldosimetry module configured to analyze an exit image by performing atleast one of a 2-D dose difference analysis and a gamma analysis. 30.The method of claim 22, wherein the real-time verification device isconfigured to process the stream of image frames to obtain absolute dosemeasurements for the field of the radiation therapy.
 31. Anon-transitory computer-readable storage medium upon which is embodied asequence of programmed instructions for verifying radiation dose from aradiation therapy system, and a computer processing system whichexecutes the sequence of programmed instructions embodied on thecomputer-readable storage medium to cause the computer processing systemto perform the steps of: irradiating a field using a radiation beam fromthe radiation therapy system; during the irradiating, acquiring acontinuous stream of image frames from an electronic portal imagingdevice (EPID) that is arranged to detect radiation exiting a patient;during the irradiating, processing the continuous stream of image framesin real-time to obtain dose measurements for the field as dose-to-watervalues; during the irradiating, determining compliance withpredetermined characteristics for the field by comparing the dosemeasurements with the predetermined characteristics; and generating anerror signal in response to a determination of non-compliance based onthe comparing.
 32. The computer-readable storage medium of claim 31,wherein: the predetermined characteristics further include a predictedtotal dose in the field after the full treatment, the comparing furthercomprises at least a difference comparison between the dose measurementand the predicted total dose, and a determination of non-compliancebased on overdose is made in response to a dose measurement exceedingthe predicted total dose.
 33. The computer-readable storage medium ofclaim 32, wherein: the predetermined characteristics include a completeirradiation area outline (CIAO) of the field, the comparing comprises ageometric comparison between the dose measurements and the CIAO, adetermination of non-compliance based on positioning is made in responseto a dose measurement being outside the CIAO, and the determiningcompliance is repeated at regular intervals after initiation of theirradiating.
 34. The computer-readable storage medium of claim 31,wherein the determining compliance is repeated at regular intervalsafter initiation of the irradiating, the regular intervals being no morethan five seconds apart.
 35. The computer-readable storage medium ofclaim 31, wherein: the predetermined characteristics include at least acomplete irradiation area outline (CIAO) of the field, the comparingcomprises at least a geometric comparison between the dose measurementsand the CIAO, the determining compliance is performed within one secondafter initiation of the irradiating, and a determination ofnon-compliance based on positioning is made in response to a a dosemeasurement being outside the CIAO.
 36. The computer-readable storagemedium of claim 31, wherein: the predetermined characteristics include apredicted total dose in the field after the full treatment and acomplete irradiation area outline (CIAO) of the field, the comparingcomprises a difference comparison between the dose measurement and thepredicted total dose, and the comparing further comprises a geometriccomparison between the dose measurements and the CIAO.
 37. Thecomputer-readable storage medium of claim 31, wherein the error signalcomprises at least one of an alert to an operator of the radiationtherapy system and a shutoff signal to the radiation therapy system thatturns off the radiation beam.
 38. The computer-readable storage mediumof claim 31, wherein the computer-readable storage medium further causesthe computer processing system to: after the irradiating, furtheranalyze the acquired EPID image frames by performing at least one of a2-D dose difference analysis and a gamma analysis; and generate a seconderror signal in response to a determination of at least one of anunderdose, overdose, or dose outside of CIAO based on the furtheranalyzing, the second error signal comprising an alert to an operator ofthe radiation therapy system or an interlock that prevents furtherirradiation of the patient using the radiation therapy system.
 39. Thecomputer-readable storage medium of claim 31, wherein thecomputer-readable storage medium further causes the computer processingsystem to display a graphical representation of the noncompliance on anexit image.
 40. The computer-readable storage medium of claim 31,wherein the obtained dose measurements are absolute dose measurementsfor the field as dose-to-water values.